The light entering the each eye first passes through the cornea (clear membrane of the eye) and then aqueous humor, iris, and lens, which converges the light rays.
After passing through the vitreous, a jelly, rays are focused on the bottom of the eye, in the sensitive part of the retina called the fovea centralis or macula, which is the center of vision clear.
In pigmented or colored layer of the retina and photoelectric photochemical changes occur that convert light rays into electrical impulses that stimulate cells called rods and cones.
Images formed on the retina are inverted image objects, which are transmitted by retinal fibers to the optic nerve. Coming out of the eyes, optic nerves traverse the vertices of the orbits and enter the skull. Below the brain, optic nerves join to form the optic chiasm, in which some nerve fibers pass from the left eye to the right, and vice versa. The fibers from the nasal portion (inner) cross each retina with the opposite side and are attached to the portion from temporal (external) on that side, thus forming optic tracts calls that penetrate the brain and arrive, by way calling optical radiation, the cerebral cortex of the occipital lobes, on the back of the brain, which initiates the actual interpretation conscious vision. The brain interprets the light and the shape of the object seen and recorded its real image, not inverted.
If you are an adult, when it is hard to see distant objects and / or looks distorted, have a headache from reading, burning, pain, tearing eyes to see far or near, eyestrain, etc..
A young child does not usually complain when he does not see well. Parents may notice if they have trouble locating or grabbing objects or do not grab objects that are given to them. Older children express discomfort while watching TV, reading, gets headaches. During school age, they may have poor performance, lack of attention, learning difficulties, isolation, etc.
It is recommended to have a comprehensive eye examination at least once every year, whether adult or child.
Nearsightedness, farsightedness and astigmatism.
The myopic eye is larger than 2.5 cm long. Light rays focus in front of the retina, so the image is blurred. The person sees near objects clearly while distant ones appear blurry or hazy. Eyeglasses are prescribed, but the lenses do not cure myopia, only help to see well. These can be either glasses or contact lenses.
The hyperopic eye is less than 2.5 cm long. Light rays focus behind the retina, so the image is blurred. The person clearly see distant objects but blurry the nearby. Corrected with lenses but they do not cure it.
In the astigmatic eye, a defect of the curvature of the cornea or the lens causes the light rays to not properly focused on the retina. Astigmatism can be farsighted, myopic, or a combination of both call mixed astigmatism. The astigmatic person complains of eyestrain, headaches, irritability, difficulty focusing on objects near and far, and blurred vision. The person may feel sharp images in a fuzzy meridian and in another, see the oval circles with taillights. Corrected with lenses but neither cure, only help to see better.
The presbyopic eye cannot focus on nearby objects due to the fact that the lens has lost elasticity and ability to change its shape or to increase its optical power. This weakening of the mechanism of accommodation, generally more evident from the age of 40, progresses to 70. It can be corrected with lenses that help you see well.
Although the fact of watching TV, does not damage your eyes by itself, it can increase the pain and eyestrain and headaches in people who need glasses. Television viewers should sit at least 2.5 to 3 meters from the screen (depending on screen size), in a room with dim light behind the screen at eye level and perpendicular to the line of sight.
The microwave oven has been a wonderful invention for cooking. However, many people believe that if used frequently, their light rays can be harmful or detrimental effects on the eyes. Indeed, this risk was related to some of the early models. The requirements of the Atomic Energy Commission of the United States are very strict and effectively protect consumers, so that the microwave radiation does not cause eye damage, as demonstrated by ophthalmologists in studies.
The increasing use of computers has led to the belief that their screens, due to its proximity, will damage the user's eyes. The observation of a computer screen will not harm the eyes, apart from producing asthenopia (eyestrain or fatigue) or other nuisances. They can even help to discover an existing refractive error.
Although these types of lights do not cause any definite eye disease, they can cause glare. The light rays reflected by an object or a shiny surface can cause eyestrain, headaches or fatigue. This can be avoided by using indirect lighting, with a slight tint lenses, colored light bulbs, or lower intensity lights.
Although poor lighting does not cause any organic eye disease, it can cause overexertion, fatigue, tiredness or headache. What is good lighting? The light should come on the left shoulder for right-handed people, and over the right shoulder for left-handed people. Avoid bad reading habits. Do not read lying in bed or in low light. If you have the habit of reading in bed before sleep, do so sitting with good lighting. Excessive reading will not damage your eyes, but can cause eyestrain.
Exposure of the eyes to bright sunlight can cause dermatitis thermal (burn or skin inflammation of the eyelids), thermal conjunctivitis (burning or inflammation of the conjunctiva), thermal keratitis (sunburn or inflammation of the cornea), or blindness temporary or permanent sunlight due to the destruction of the retina or macula by heat. There have been cases of solar blind people who have looked directly at a solar eclipse without proper protection. They should wear dark lens with 100% UV protection, sun exposure to prevent damage.
Drinking in moderation will not damage your eyes, but excessive consumption can cause redness, double vision or visual hallucinations. Methyl alcohol (wood) causes blindness by its toxic effect destroying optic nerve.
Neither eyewash cures an infection or an eye disease, but alleviates eye irritation and redness temporarily decreases. The eyecup or eyewash is no longer used to treat or wash the eye with eye drops, as it can damage the eye, carrying microbes that infect the eyelashes or eyelids, or transmitting infection from one eye to another or from one person to another. You can use gauze pads with warm or cold water, which should be discarded after use.
The makeup will not harm the eyes, unless a particle is introduced between the lids accidentally. Some people may be allergic to substances containing products for makeup, but the use of hypoallergenic cosmetics remedies this situation in many cases.
To rub eyes do not cause blindness or eye defects, but can transmit an eye infection. In people with diabetes or other diseases that affect blood vessels, eye rubbing can break fragile vessels and cause sub conjunctively hemorrhage, retinal or vitreous. If a foreign body penetrates between the eyelids, rubbing can irritate sensitive or seriously injure the cornea.
Moderate consumption of cigarettes does not affect the eyes, but the smoke itself can act as an irritant and cause burning and redness.
Vitamin A, found in carrots, is important in the function of the retina because it contributes to the production of the visual purple. This substance is essential to see well at night. However, eating lots of carrots will not improve night blindness, unless it is due to a deficiency of vitamin A. Poor vision for refractive error, cataracts, glaucoma or strabismus cannot be prevented, delayed or enhanced by vitamin A by eating carrots.
It has been suggested that eye exercises can cure nearsightedness, farsightedness or astigmatism and eliminates the use of lenses. That is not true. These refractive defects depend on the shape of the cornea and / or the length of the eyeball, so can only be corrected by suitable lenses that focus the light rays on the retina precisely and thus produce a sharp image. The exercises will not or cannot do that, nor can improve cataracts, glaucoma or color blindness. The only real therapeutic value eye exercises lies in improving muscle imbalances as weak convergence, or inability to get eyes, for example to see with both eyes toward the nose. The exercises tend to reinforce internal rectus extraocular muscles, thereby improving the convergence point maximum, for example its ability to cross the eyes. Orthoptic eye exercises improve vision and helps stimulate binocular depth perception.
We've all heard of the evil eye and its terrible consequences. However, it is more than an absurd tale witches. It is also absolutely false idea that a child will be born with certain defects if her mother is shocked to see snakes or deformed people during pregnancy
To me, the most important thing, are your eyes.
Dr. Gonzalo Anzueto Ophthalmologist
